Rechargeable lithium-ion battery with an anode structure containing a porous region

ABSTRACT

Rechargeable lithium-ion batteries that have a high-capacity are provided. The lithium-ion batteries contain an anode structure that is of unitary construction and includes a non-porous region and a porous region including a top porous layer (Porous Region  1 ) having a first thickness and a first porosity, and a bottom porous layer (Porous Region  2 ) located beneath the top porous layer and forming an interface with the non-porous region. At least an upper portion of the non-porous region and the entirety of the porous region are composed of silicon, and the bottom porous layer has a second thickness that is greater than the first thickness, and a second porosity that is greater than the first porosity.

BACKGROUND

The present application relates to a rechargeable battery. Moreparticularly, the present application relates to a high-capacityrechargeable lithium-ion battery including an anode structure composedof a substrate that includes a porous semiconductor region with twodifferent porosities and a non-porous semiconductor region locatedbeneath the porous semiconductor region.

In recent years, there has been an increased demand for electronicdevices such as, for example, computers, mobile phones, trackingsystems, scanners, medical devices, smart watches, power tools, remotesystems and sensors, electric vehicles, internet of things (IOT) andfitness devices. One drawback with such electronic devices is the needto include a power supply within the device itself. Typically, a batteryis used as the power supply of such electronic devices. Batteries musthave sufficient capacity to power the electronic device for at least thelength that the device is being used. Sufficient battery capacity canresult in a power supply that is quite heavy and/or large compared tothe rest of the electronic device. As such, smaller sized and lighterweight power supplies with sufficient energy storage are desired. Suchpower supplies can be implemented in smaller and lighter weightelectronic devices in combination with lithium ion materials acting asthe charge carrier; as lithium is the lightest and most electropositivecharge carrier ion in the Periodic Table of Elements, lithium ionbatteries and capacitors are considered the best fit for smaller, moreenergy dense energy storage devices.

Aside from the demand for lightweight energy storage devices that yieldhigh energy density (high capacity), the need for faster charge rates(i.e., high speed charging kinetics) is also a current demand in theconsumer market. For the next generation of batteries, it would bedesirable if the battery was able to be fully charged in ten minutes orless in order to meet the needs of consumers in markets such as electricvehicles, portable telecommunications, IOT, and sensors. In the case ofelectric vehicles, if a consumer must wait longer than ten minutes tocharge his/her vehicle, the battery powered electric vehicle may imposea limitation on the user's timeline and consequently, their travelrange. Hence, fast charge rates of batteries used in the electricvehicles market would help create a viable electric vehicle market thatwould compete with and perhaps substitute for gas-powered automobiles.

Another drawback of conventional batteries is that some of the batteriescontain potentially flammable and toxic materials that may leak causingsafety hazards and expensive product recalls. As a result, thesebatteries may be subject to governmental regulations and cause damage toproduct reputation. The battery leakage risks can increase due to cracksforming within these batteries. These cracks are most likely caused byinternal stress due to the battery charge/discharge cycles.

In addition and in the case of batteries containing a solid-stateelectrolyte, there is evidence that battery lifetime performance isdecreased due to dendrite formation within these batteries. Dendritesize increases over the lifetime of the battery and most likely relatesto the number of charge/discharge cycles of the battery as well. Asdendrites form within the battery and grow larger over time, thedendrites tend to electrically short the internal components of thebattery, causing battery failure.

With the advent of lithium metal charge hosting electrodes, whichprovide stable, charge hosting of lithium metal and facilitate thereversible ionization mechanism of lithium ions into lithium metal, andvice versa, sustainable all-solid state or semi-solid state lithium ionbatteries are attainable for mass production in consumer markets.Lithium metal maintains a theoretical energy capacity of 3850 mAh/g,whereas silicon-based lithium-hosting electrode materials maintain atheoretical capacity of 4200 mA/g. Both of these materials acting as ananode, for example, are greater than ten times the theoretical capacityof conventional graphitic anode materials (372 mAh/g). However, thesebatteries still have the risk of cracking, leakage, and internaldendrite failure.

Hence there is a need for an improved lithium-ion battery to provide anelectrical power supply that has reduced charge times, has higherstorage capacities, and is safe and rechargeable over manycharge/discharge life cycles with reduced risk of cracking, leakage, andfailure due to dendrite growth within the battery.

SUMMARY

Rechargeable lithium-ion batteries that maintain a high-capacity (i.e.,a capacity of 100 mAh/g or greater) are provided. In some embodiments,the rechargeable lithium-ion batteries of the present application mayalso exhibit an increased lifetime, increased numbers ofcharge/discharge cycles, reduced charge time (i.e., a fast charge rate),a reduction of volume expansion and/or deformation during cycling, areduction of dendrite and crack formation, and/or reduced batteryleakage due to cracking.

The rechargeable lithium-ion battery of the present application includesan electrolyte region located between a lithium-containing cathodematerial layer and an anode structure. The anode structure is of unitaryconstruction (i.e., a monolith structure) and includes a non-porousregion and a porous region. The porous region comprises a top porouslayer (Porous Region 1) having a first thickness and a first porosity,and a bottom porous layer (Porous Region 2) having a second porositythat is greater than the first porosity and a second thickness that isgreater than the first thickness. The bottom porous layer (i.e., PorousRegion 2) is located beneath the top porous layer (i.e., Porous Region1) and forms an interface with the non-porous region. Also, at least anupper portion of the non-porous region and the entirety of the porousregion are composed of silicon.

In another aspect of the present application, a method of making theaforementioned anode structure for a rechargeable lithium-ion battery isprovided. The method includes anodic etching a substrate that includesat least an upper region composed of p-doped silicon. In one embodiment,the relative depth, pore structure and surface area of the anodestructure including Porous Regions 1 and 2 is controlled through theapplied conditions of the method of the present application.

Another aspect of the present application shows operational changes tothe anode structure for a rechargeable battery during battery charge anddischarge cycles. The anode structure and the battery structure of thepresent application charge in unique ways that exhibit reduced internalstresses and reduced dendrite growth over the battery lifetime. Withoutwishing to be bound by any theory, it is believed that the chargingoperation of the present application contributes to reduced levels ofinternal battery stress and reduced incidence of anode structurecracking.

In yet another aspect of the present application, cathode materialscontaining a specific grain size and density of grain boundaries or acolumnar microstructure are used in combination with the present anodestructure. The anode structure of the present application cansustainably plate lithium materials sourced from the respective cathodematerials of various dimensions and mass. In particular, since the anodestructure of the present application facilitates apparent lithiumplating during charging, and lithium stripping during discharging, highcapacity battery cells can be readily fabricated.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a cross sectional view of an exemplary rechargeablelithium-ion battery in accordance with a first embodiment of the presentapplication.

FIG. 2 is a cross sectional view of another exemplary rechargeablelithium-ion battery in accordance with a second embodiment of thepresent application.

FIG. 3 is a cross sectional view of an exemplary rechargeablelithium-ion battery in accordance with a third embodiment of the presentapplication.

FIG. 4 is a cross sectional view of an exemplary rechargeablelithium-ion battery in accordance with a fourth embodiment of thepresent application.

FIG. 5 is a cross sectional view of an exemplary rechargeablelithium-ion battery in accordance with a fifth embodiment of the presentapplication.

FIGS. 6A-6B are cross sectional views of exemplary rechargeablelithium-ion batteries in accordance with a sixth embodiment of thepresent application.

FIG. 7A is a schematic illustration of a method of forming the anodestructure of the present application starting from a p-type crystallinesilicon substrate prior to anodization, and the anode structure afteranodization.

FIG. 7B is a cross sectional transmission electron micrograph (TEM) of aporous silicon anode structure displaying two distinct porous regionsupon anodization.

FIG. 8A is a high resolution transmission electron micrograph (HRTEM) ofthe porous silicon anode structure illustrating the thickness of PorousRegion 1.

FIG. 8B is a secondary ion mass spectrometry (SIMS) spectrum of aninitial ˜30 nm of a porous silicon anode structure corresponding toPorous Region 1 and an initial ˜90 nm of the same silicon anodestructure corresponding to Porous Region 2.

FIGS. 9A-9F represent a flow diagram showing the anode structure prioroperational use (FIG. 9A) and during operational use, with a seed layerforming during a charge cycle (FIG. 9B), lithium plating occurring aftercontinuous charging (FIG. 9C), and lithium stripping occurring duringdischarge (FIG. 9F), with SEM images of a porous silicon anode structureafter 5 cycles when utilizing a liquid electrolyte (FIG. 9D) and anotherSEM image of a porous silicon anode structure after ˜250 cycles whenutilizing a liquid electrolyte (FIG. 9E).

FIGS. 10A-10C are SEM images for an all solid-state lithium ion batteryin accordance with the present application and containing a structuresimilar to that shown in FIG. 1 in which the electrolyte region is asolid-state material, wherein FIG. 10A is a SEM of the structure priorto galvanostatic-or-potentiostatic-induced charge or discharge, FIG. 10Bis another SEM of the structure after 6 charge and discharge cycles, andFIG. 10C is yet another SEM image of the structure after 67 charge anddischarge cycles.

FIG. 11 is a flow chart illustrating one embodiment for making the anodestructure of the present application.

DETAILED DESCRIPTION

The present application will now be described in greater detail byreferring to the following discussion and drawings that accompany thepresent application. It is noted that the drawings of the presentapplication are provided for illustrative purposes only and, as such,the drawings are not drawn to scale. It is also noted that like andcorresponding elements are referred to by like reference numerals.

In the following description, numerous specific details are set forth,such as particular structures, components, materials, dimensions,processing steps and techniques, in order to provide an understanding ofthe various embodiments of the present application. However, it will beappreciated by one of ordinary skill in the art that given thisdisclosure, there are various alternative embodiments of the presentapplication that may be practiced without providing further specificdetails. In other instances, well-known structures or processing stepscould be used in combination with and/or using the concepts of thepresent invention. These structures and steps have not been described indetail in order to avoid obscuring the present application.

It will be understood that when an element as a layer, region orsubstrate is referred to as being “on” or “over” another element, it canbe directly on the other element or intervening elements may also bepresent. In contrast, when an element is referred to as being “directlyon” or “directly over” another element, there are no interveningelements present. It will also be understood that when an element isreferred to as being “beneath” or “under” another element, it can bedirectly beneath or under the other element, or intervening elements maybe present. In contrast, when an element is referred to as being“directly beneath” or “directly under” another element, there are nointervening elements present.

As stated above, rechargeable lithium-ion batteries that have ahigh-capacity (i.e., a capacity of 100 mAh/g or greater) are provided.In some embodiments, the rechargeable lithium-ion batteries of thepresent application may also exhibit an increased lifetime and/or fastercharge rate and/or a reduction of volume expansion and/or deformationduring charge/discharge cycling. The rechargeable lithium-ion batteriesof the present application contain an anode structure that is engineeredto increase the capacity, and in some instances, even the charge rate,of the battery (compared to conventional lithium-ion batteries that lackthe anode structure of the present application).

In one aspect of the present application, a rechargeable lithium-ionbattery is provided that includes an anode structure of unitaryconstruction. Notably, the anode structure includes a non-porous regionand a porous region comprising a top porous layer (Porous Region 1)having a first thickness and a first porosity, and a bottom porous layer(Porous Region 2) having a second thickness that is greater than thefirst thickness, and a second porosity that is greater than the firstporosity. The bottom porous layer (Porous Region 2) is located beneaththe top porous layer (Porous Region 1) and forms an interface with thenon-porous region. In the anode structure of the present application, atleast an upper portion of the non-porous region and the entirety of theporous region (including Porous Regions 1 and 2) are composed ofsilicon.

Methods of making the battery, methods of using the battery, structuralfeatures of the battery during use, and battery structures with cathodesenabling fast charging rates are also presented. The anode structure ofthe present application can be used as an element within variousconventional 2-dimensional and 3-dimensional battery configurations.

It is believed that the anode structure of the present application isstronger than those in the prior art because Porous Region 1 containssmaller pore sizes on average compared with Porous Region 2. In someembodiments, the anode structure which includes a larger non-porousregion together with Porous Region 1 and Porous Region 2 ismechanically, electrically, and chemically made of the samesemiconductor material (i.e., the anode structure is of monolithconstruction). Thus, a mechanically stronger anode structure which isinterconnected though out—at the atomic level, particularly for siliconsubstrates that are crystalline in composition—is provided.

It is also believed, that during the initial lithiation of the anodestructure of the present application, an upper portion of Porous Region2 becomes partially lithium containing, and the lower portion of PorousRegion 2 is substantially devoid of lithium. During this process, athin, seed layer begins to form, where the composition of the seed layeris composed of lithium rich material and silicon material andconsequently forms a planar lithium metal-dense layer on top of PorousRegion 1. This seed layer significantly reduces the migration of lithiumions deeper into Porous Region 2 of the anode structure (and at reducedlithium ion concentrations within Porous Region 2.). Hence, theformation of the thin seed layer on/in Porous Region 1 impedes furtherlithiation of Porous Region 2 and consequentially minimizes mechanicalstress of the entire electrode due to suppression of further lithiationdeeper into Porous Region 2 and the non-porous region.

As lithium migrates into the anode structure, the volume regions wherethe lithium combines with the silicon of the anode structure expand.This volume can expand up to 400 percent the original anode structurevolume. Therefore, the anode structure of the present applicationenables a reduction of the volume expansion during the lifetime (entirecharge/discharge cycles) of the rechargeable lithium-ion battery,resulting in reduced internal stress over the battery's entire use.

Since lithium combines with the silicon in the Porous Regions 1 and 2,the voids in these porous regions accommodate the increase of volume inthese portions of the anode structure, further reducing the mechanicalstresses of charge and discharge.

In addition, as the battery charges/discharges throughout the batterylifetime, the lithium maintains a seed layer of lithium in combinationwith silicon atoms present in the porous region of the anode structure;this seed layer may be referred to hereinafter as a lithium-containingseed layer. During seed layer formation, a small fraction of lithium(less than 10% of theoretical capacity) penetrates into and throughPorous Region 1 and partially penetrates through Porous Region 2. Thisprocess is relatively slow if not electrochemically induced, and theprocess is faster if galvanostatically or potentiostatically induced.The lithium further forms a thin layer of metallic lithium on top ofPorous Region 1 as the lithium accumulates on the previously depositedlithium-containing seed layer on/in Porous Region 1, expands the volumein the Porous Region 1 and minimizes lithium from further migratingdeeper into the anode structure of the present application by physicallyclosing of the pores in Porous Region 1 and by the lithium concentrationin the seed layer and metallic layer providing an electrostatic barrierto further penetration of lithium into the anode structure of thepresent application.

The fully formed seed layer minimizes further lithium migration into theanode structure during subsequent charge/discharge cycles of thebattery, thus reducing the cyclic mechanical stresses of volumeexpansion and contraction during the charge/discharge cycles over muchof the battery's lifetime and commensurately reducing the stresses inthe anode structure over the battery's life.

Since the fully formed seed layer inhibits the migration of lithium ionsinto the anode structure, the following is observed: (i) lithium ionsmoving toward the anode structure from the cathode and electrolyteregions of the battery during a charge cycle increase the thickness ofthe lithium metal layer above the seed layer; and (ii) lithium ionsmoving away from the anode structure from the cathode and electrolyteregions of the battery during a discharge cycle decrease the thicknessof a lithium metal layer above the seed layer. However, lithiumdiffusion is minimized through the fully formed seed layer during thesubsequent charge/discharge cycles of the battery, as opposed to that inthe prior art. As a result of the anode structure of the presentapplication, the lithium primarily deposits on the seed layer (forexample, via ion-plating); at a much reduced amount, within PorousRegion 2; but not in any significant amount in the non-porous region ofthe anode structure. As a result, a very large volume of the anodestructure, i.e., the non-porous region of the anode structure,substantially does not absorb lithium during the charge/discharge cyclesand therefore does not undergo significant volume expansion andcontraction which cause cracking, and possible leakage, as observed inbatteries not containing the anode structure of the present application.

It is speculated that the thin, seed layer once formed does not changemuch during the charge/discharge cycle of the battery. The porosity ofPorous Region 1 is chosen such that the volume expansion in the topporous layer of the anode structure due to chemical bonding with lithiumduring the seed layer formation does not cause undue stress in PorousRegion 1.

Applicant has experimental evidence showing that the seed layer forms asmooth, planar surface on which addition (and removal) of lithium ionsduring charge (discharge) cycles of operation cause a metallic lithiummetal layer to grow (shrink) in thickness while maintaining a relativelysmooth and planar surface over the life of the battery with higherprobability of suppression of dendrite growth.

Referring now to FIG. 1, there is illustrated an exemplary rechargeablelithium-ion battery in accordance with a first embodiment of the presentapplication. The exemplary rechargeable lithium-ion battery illustratedin FIG. 1 includes a battery material stack of an anode currentcollector 10, an anode structure 12, an electrolyte region 18, alithium-containing cathode material layer 20, and a cathode currentcollector 22. Although the present application depicts the anode currentcollector 10 as the bottommost material layer of the lithium-ionbattery, the present application also contemplates embodiments in whichthe cathode current collector 22 represents the bottommost materiallayer of the lithium-ion battery of the present application. Otherorientations for the lithium-ion battery are also possible and are notexcluded from the present application.

In some embodiments, the rechargeable lithium-ion battery of the presentapplication may be formed upon a base substrate (not shown). If present,the base substrate may include any conventional material that is used asa substrate for a lithium-ion battery. In one embodiment, the basesubstrate may include a silicon-containing material and/or any othermaterial having semiconductor properties. The term “silicon-containingmaterial” is used throughout the present application to denote amaterial that includes silicon and has semiconducting properties.Examples of silicon-containing materials that may be employed as thebase substrate for the rechargeable lithium ion battery include silicon(Si), a silicon germanium alloy (SiGe), or a carbon-doped silicon-basedalloy. In one embodiment, the base substrate for the rechargeablelithium-ion battery is a bulk semiconductor substrate. By “bulk” it ismeant that the base substrate is entirely composed of at least onesemiconductor material. In one example, the base substrate may beentirely composed of silicon which may be single crystalline. In someembodiments, the bulk semiconductor substrate may include a multilayeredsemiconductor material stack including at least two differentsemiconductor materials. In one example, the multilayered semiconductormaterial stack may comprise, in any order, a stack of Si and a silicongermanium alloy. In another embodiment, the multilayered semiconductormaterial may comprise, in any order, a stack of Si and single ormultiple silicon-based alloys, such as silicon-germanium or carbon-dopedsilicon-based alloys.

In other embodiments, the base substrate for the lithium-ion battery maybe a current collector such as, for example, aluminum (Al), aluminumalloy, titanium (Ti), tantalum (Ta), tungsten (W), or molybdenum (Mo),copper (Cu), nickel (Ni), platinum (Pt) or any alloys of thesematerials.

In some embodiments, the base substrate may have a non-textured (flat orplanar) surface. The term “non-textured surface” denotes a surface thatis smooth and has a surface roughness on the order of less than 100 nmroot mean square as measured by profilometry or Atomic Force Microscopy.In yet another embodiment, the base substrate may have a texturedsurface. In such an embodiment, the surface roughness of the texturedsubstrate can be in a range from 100 nm root mean square to 100 μm rootmean square as also measured by profilometry or Atomic Force Microscopy.Texturing can be performed by forming a plurality of etching masks(e.g., metal, insulator, or polymer) on the surface of a non-texturedsubstrate, etching the non-textured substrate utilizing the plurality ofmasks as an etch mask, and removing the etch masks from the non-texturedsurface of the substrate. In some embodiments, the textured surface ofthe base substrate is composed of a plurality of high surface area3-dimensional features. In some embodiments, a plurality of metallicmasks are used, which may be formed by depositing a layer of a metallicmaterial and then performing an anneal. During the anneal, the layer ofmetallic material melts and balls-ups such that de-wetting of thesurface of the base substrate occurs.

Referring back to FIG. 1, the anode current collector 10 that may beemployed in the present application includes any metallic anode-sideelectrode material such as, for example, titanium (Ti), platinum (Pt),nickel (Ni), copper (Cu), aluminum (Al) or titanium nitride (TiN). Theanode collector 10 may include layer of a metallic anode-side electrodematerial, or a material stack of at least two different metallicanode-side electrode materials. In one example, the anode currentcollector 10 includes a stack of, from bottom to top, nickel (Ni) andcopper (Cu). The anode current collector 10 may have a thickness from 10nm to 50 □m. Other thicknesses that are lesser than, or greater than,the aforementioned thickness values may also be used for the anodecurrent collector 10. The anode current collector 10 can be formedutilizing a deposition process including, for example, chemical vapordeposition (CVD), plasma enhanced chemical vapor deposition (PECVD),evaporation, sputtering, plating, or mechanically attached metallicfoil. For improved contact resistance, alloying of the metallicanode-side electrode material with a semiconductor material base wouldbe preferred. Alloying may be achieved by performing a silicidationprocess as is known to those in the semiconductor industry.

Anode structure 12 is provided to a surface of the anode currentcollector 10. The anode structure 12 includes a non-porous region 14,and a porous region (16, 17) that has two layers having differentporosities and thicknesses located on the non-porous region 14. Theporous region of the anode structure includes a bottom porous layer 16(i.e., Porous Region 2) and a top porous layer 17 (i.e., Porous Region1). The non-porous region 14 and the porous region (16, 17) are ofunitary construction. In one embodiment, the non-porous region 14 has afirst surface that is in direct physical contact with a surface ofPorous Region 2 (i.e., the bottom porous layer 16), and a secondsurface, opposite the first surface, that is in direct physical contactwith the anode-current collector 10. The non-porous region 14 is thelargest portion, by volume, of the anode structure 12. In someembodiments, the non-porous region 14 of the anode structure 12 may havea thickness from 5 μm to 700 μm.

Porous Region 1 (i.e., the top porous layer 17) has a first porosity anda first thickness, and Porous Region 2 (i.e., the bottom porous layer16) has a second porosity and a second thickness. In order toaccommodate volume changes during charging and discharging, the porousregion (16, 17) is engineered such that the second porosity and secondthickness are greater than the first porosity and first thickness,respectively. In one embodiment, the second porosity has an average poreopening of greater than 3 nm, and the second thickness is between 0.1 μmto 20 μm, while the first porosity has an average pore opening of lessthan 3 nm, and the first thickness is 50 nm or less. Without wishing tobe bound by any theory, it is believed that the relatively smalldiameter of pores contained in Porous Region 1 facilitates the formationof a planarized lithium-containing seed layer (to be described ingreater detail herein below).

In the present application, the porosity can be a measure of the volumepercentage of the pores (void region in the silicon) divided by thetotal volume of the porous region (16, 17). The porosity may be measuredusing techniques well known to those skilled in the art including, forexample, SEM, RBS, X-ray Diffraction (XRD), Nuclear Magnetic Resonance(NMR), Raman Spectroscopy, gas-on-solid adsorption (porosimetry),mercury space filling porosimetry, density functional theory (DFT), orBrunauer-Emmett-Teller (BET).

It is noted that the present application avoids a porous region (16, 17)that has a porosity that is 30% or greater, which as in the prior art,has a tendency to be brittle and may crack during use such that batteryfailure may occur.

Without wishing to be bound by any theory, it is speculated that theporous region (16, 17) has a porosity such that a sufficient open spacewithin the porous region (16, 17) exists to accommodate volume expansion(i.e., swelling) and/or deformation of both Porous Region 1 (i.e., thetop porous layer 17) and to a lesser extent Porous Region 2 (i.e., thebottom porous layer 16). This is particularly true in the formation of alithium-containing seed layer, described in greater detail herein below,in Porous Region 1 (i.e., the top porous layer 17) in the initialoperation of a rechargeable lithium-ion battery.

Porous Region 2 (i.e., the bottom porous layer 16) of the anodestructure 12 of the present application has a compressive stress from0.02 percent to 0.035 percent. Compressive stress can be determined byX-ray Diffraction or other optical or spectroscopic techniques.

As mentioned above, Porous Region 1 (i.e., the top porous layer 17),Porous Region 2 (i.e., the bottom porous layer 16) and the non-porousregion 14 of the anode structure 12 are of unitary construction. Thus,non-porous region 14 and porous region (16, 17) are electrically,chemically and mechanically part of a same anode structure. In someembodiments, the Porous Region 1 (i.e., the top porous layer 17), PorousRegion 2 (bottom porous layer 16) and the non-porous region 14 areentirely composed of silicon. In this embodiment, the anode structure 12is created by efficient method steps. In addition, and in embodiments inwhich the entire anode structure 12 is made of the same semiconductormaterial (i.e., Si) there are no mechanical stresses or additionalelectrical resistances within the anode structure 12 that might becaused by interfaces between dissimilar materials. In one example, theanode structure 12 including the non-porous region 14 and porous region(16, 17) has a three-dimensional (3D) lattice framework composed of ap-type crystalline silicon material. The term “p-type” refers to theaddition of impurities to an intrinsic silicon material that createsdeficiencies of valence electrons. In a silicon-containing siliconmaterial, examples of p-type dopants, i.e., impurities, include, but arenot limited to, boron, aluminum, gallium and indium.

In some embodiments, at least an upper portion of the non-porous region14 of anode structure 12 that forms an interface with Porous Region 2(i.e., the bottom porous layer 16) as well as the entire porous region(16, 17) are composed of a same material such as, for example, p-typedoped silicon material, while a lower portion of the non-porous region14 may be composed of a different semiconductor material than the upperportion of the non-porous region 14 of anode structure 12 that forms aninterface with Porous Region 2 (i.e., the bottom porous layer 16) aswell as the entire porous region (16, 17). For example, the lowerportion of the non-porous region 14 that is present beneath the porousregion (16, 17) may include doped silicon having a different dopantconcentration than the original p-type doped silicon used to provide theanode structure 12, or a silicon germanium alloy containing less than 10atomic percent germanium.

In some embodiments and due to the simplicity and manufacturability ofsingle crystalline material, the silicon material that provides at leastan upper portion of the non-porous region 14 of anode structure 12 thatforms an interface with Porous Region 2 (i.e., the bottom porous layer16) as well as the entire porous region (16, 17) is single crystalline.In some embodiments, the cost of the process can be reduced andcontrolled by using lower grade silicon and by adjusting the siliconthickness and simplified crystal growth techniques (as is the caseobserved in the solar industry).

The anode structure 12 of the present application can be formedutilizing an anodic etching process as defined in greater detail hereinbelow (see, for example, FIG. 11).

The electrolyte that can be present in the electrolyte region 18 mayinclude any conventional electrolyte that can be used in a rechargeablelithium-ion battery. The electrolyte may be a liquid electrolyte, asolid-state electrolyte, a gel type electrolyte, a polymer electrolyte,a semi-solid electrolyte, an electrolyte which originally is a liquid,but then is subjected to conditions which transforms its phase into asolid or semi-solid, or any combination thereof such as, for example, acombination of a liquid electrolyte and a solid state electrolyte. Insome embodiments, the electrolyte region 18 is composed entirely of asolid-state electrolyte. In other embodiments, the electrolyte region 18may include a solid-state electrolyte and a liquid electrolyte. Theelectrolyte is between Porous Region 1 (i.e., the top porous layer 17)and the lithium-containing cathode material layer 20.

In some embodiments, the electrolyte region 18 is a solid-stateelectrolyte that is composed of a polymer based material or an inorganicmaterial. In other embodiments, the electrolyte region 18 is asolid-state electrolyte that includes a material that enables theconduction of lithium-ions. Such materials may be electricallyinsulating and ionically conducting. Examples of materials that can beemployed as the solid-state electrolyte include, but are not limited to,lithium phosphorus oxynitride (LiPON) or lithium phosphosilicateoxynitride (LiSiPON), thio-LiSiCoN electrolytes (e.g., Li₂S—P₂S₅ in anyratio), Li₁₀SnP₂S₁₂, LiSiCoN-like electrolytes (e.g., Li₁₀GeP₂S₁₂),Argyrodite electrolytes (e.g., Li₆PS_(s)Br), Garnet Electrolytes (e.g.,Li₆₅₅La₃Zr₂Ga_(0.15)O₁₂), NaSiCoN-like electrolytes (e.g.,Li_(1.3)Al_(0.3)Ti_(1.7)(P^(O) ₄)₃), Li-Nitride electrolytes (e.g.,Li₃N), Li-Hydride Electrolytes (e.g., Li₂NH), or Pervoskite Electrolytes(e.g., Li_(0.34)La_(0.51)TiO_(2.94)).

In embodiments in which a liquid electrolyte is employed in theelectrolyte region 18, a separator, not shown, may be used. A separatormay also be used in embodiments in which two dissimilar electrolytes arepresent in the electrolyte region 18. When a separator is employed, theseparator may include one or more of a flexible porous material, a gel,or a sheet that is composed of cellulose, cellophane, polyvinyl acetate(PVA), PVA/cellulous blends, polyethylene (PE), polypropylene (PP) or amixture of PE and PP. The separator may also be composed of inorganicinsulating nano/microparticles.

In embodiments in which a solid-state electrolyte layer is employed asthe electrolyte region 18, the solid-state electrolyte may be formedutilizing a deposition process such as, sputtering, solution deposition,hot pressing, cold pressing, slurry casting followed by controlledtemperature and pressure conditions or plating. In one embodiment, thesolid-state electrolyte is formed by sputtering utilizing anyconventional target source material in conjunction with reactive orinert gasses. For examples, sputtering may be performed in the presenceof at least a nitrogen-containing ambient, in forming the LiPONelectrolyte. In some embodiments, the nitrogen-containing ambient isused neat, i.e., non-diluted. In other embodiments, thenitrogen-containing ambient can be diluted with an inert gas such as,for example, helium (He), neon (Ne), argon (Ar) and mixtures thereof.The content of nitrogen (N₂) within the nitrogen-containing ambientemployed is typically from 10% to 100%, with a nitrogen content withinthe ambient from 50% to 100% being more typical.

The lithium-containing cathode material layer 20 may include alithium-containing material such as, for example, a lithium-based mixedoxide. Examples of lithium-based mixed oxides that may be employed asthe lithium-containing cathode material layer 20 include, but are notlimited to, lithium cobalt oxide (LiCoO₂), lithium nickel oxide(LiNiO₂), lithium manganese oxide (LiMn₂O₄), lithium vanadium pentoxide(LiV₂O₅), lithium nickel manganese cobalt (NMC), nickel cobalt aluminumoxide (NCA), any combination of sulfur-based materials with lithium andother structure supporting elements such as iron, or lithium ironphosphate (LiFePO₄). The lithium-containing cathode material layer 20may have a thickness from 10 nm to 50 μm. Other thicknesses that arelesser than, or greater than, the aforementioned thickness values mayalso be used for lithium-containing cathode material layer 20.

In some embodiments, the lithium-containing cathode material layer 20may be formed utilizing a deposition process such as, sputtering, slurrycasting or plating. In one embodiment, the lithium-containing cathodematerial layer 20 is formed by sputtering utilizing any conventionalprecursor source material or combination of precursor source materials.In one example, a lithium precursor source material and a cobaltprecursor source material are employed in forming a lithium cobalt mixedoxide. Sputtering may be performed in an admixture of an inert gas andoxygen. In such an embodiment, the oxygen content of the inertgas/oxygen admixture can be from 0.1 atomic percent to 70 atomicpercent, the remainder of the admixture includes the inert gas. Examplesof inert gases that may be used include argon, helium, neon, nitrogen orany combination thereof in conjunction with oxygen.

In some embodiments, the lithium-containing cathode material layer 20,may be formed by slurry casting, which may contain a mixture ofelectrochemically active [cathode materials, electron-conductingmaterials (e.g., carbon-based materials)] and inactive (bindermaterials) components. The thickness of such layers could range from 5μm to 500 μm. These slurries may also have an electrolyte component inthe mixture, along with a lithium based salt(s).

The cathode current collector (i.e., cathode-side electrode) 22 mayinclude any metallic cathode-side electrode material such as, forexample, titanium (Ti), platinum (Pt), nickel (Ni), aluminum (Al) ortitanium nitride (TiN). The cathode current collector 22 may include asingle layer of a metallic cathode-side electrode material, or amaterial stack including at least two different metallic cathode-sideelectrode materials. In one example, the cathode current collector 22includes a stack of, from bottom to top, titanium (Ti), platinum (Pt)and titanium (Ti). In one embodiment, the metallic electrode materialthat provides the cathode current collector 22 may be the same as themetallic electrode material that provides the anode current collector10. In another embodiment, the metallic electrode material that providesthe cathode current collector 22 may be different from the metallicelectrode material that provides the anode current collector 10. Thecathode current collector 22 may have a thickness within the rangementioned above for the anode current collector 10. The cathode currentcollector 22 may be formed utilizing one of the deposition processesmentioned above for forming the anode current collector 10. Forslurry-based cathode materials, metal foils may be employed during thecasting process.

Referring now to FIG. 2, there is illustrated another exemplaryrechargeable lithium-ion battery in accordance with a second embodimentof the present application. The exemplary lithium-ion batteryillustrated in FIG. 2 is similar to the rechargeable lithium-ion batterystack shown in FIG. 1 except that an interfacial additive material layer24 is positioned between the Porous Region 1 (i.e., the top porous layer17) of the anode structure 12 and the electrolyte region 18.Specifically, the exemplary rechargeable lithium-ion battery illustratedin FIG. 2 includes a battery material stack of an anode currentcollector 10, as defined above, an anode structure 12, as defined above,an interfacial additive material layer 24 to be defined in greaterdetail herein below, an electrolyte region 18, as defined above, alithium-containing cathode material layer 20, as defined above, and acathode current collector 22, as defined above. The battery materialstack shown in FIG. 2 may have other orientations besides that shown inFIG. 2. For example, it may be flipped 180°.

An interfacial additive (such as a dielectric material) layer 24 ispresent on the exposed surface of Porous region 1 (i.e., the top porouslayer 17) of the anode structure 12; layer 24 may be a single layeredstructure or a multilayered structure. The interfacial additive materiallayer 24 may include any interfacial additive material layer such as,for example, a carbon based material, or gold or a dielectric materialoxide such as, for example, aluminum oxide. The interfacial additivematerial may be a mixture with any combination of electricallyinsulating as well as Li-ion ionic-conducting components, such as butnot limited to LiNbO₃, LiZrO₂, Li₄SiO₄, or Li₃PO₄. The interfacialadditive material layer 24 may have a thickness from 1 nm to 50 nm. Theinterfacial additive material layer 24 may be formed utilizing adeposition process including, for example, chemical vapor deposition,plasma enhanced chemical vapor deposition, or atomic layer deposition.The interfacial additive material layer 24 can enable a high magnitudeof chemical and physical interconnectivity between electrolyte andelectrode layers under repeated electrochemical conditioning. Theinterfacial additive material layer 24 can maintain structural rigidityfor interfacial overlap, which enables high ionic conductivity andreduces the internal resistance of the cell. In addition, theinterfacial additive material layer 24 can provide electrical insulationat the interfaces of concern, preventing the leaking or shorting of thecell through spatial control of electrically conductive componentswithin the battery. The interfacial additive material layer 24, asdescribed above, could be continuous or patterned.

Referring now to FIG. 3, there is illustrated another exemplaryrechargeable lithium-ion battery in accordance with a third embodimentof the present application. The exemplary rechargeable lithium-ionbattery illustrated in FIG. 3 is similar to the rechargeable lithium-ionbattery stack shown in FIG. 1 except that an interfacial additivematerial layer 26 is positioned between the electrolyte region 18 andthe lithium-containing cathode material layer 20. Specifically, theexemplary rechargeable lithium-ion battery illustrated in FIG. 3includes a battery material stack of an anode current collector 10, asdefined above, an anode structure 12, as defined above, an electrolyteregion 18, as defined above, an interfacial additive material layer 26to be defined in greater detail herein below, a lithium-containingcathode material layer 20, as defined above, and a cathode currentcollector 22, as defined above. The battery material stack shown in FIG.3 may have other orientations besides that shown in FIG. 3. For example,it may be flipped 180°.

The interfacial additive material layer 26 may include any of theinterfacial additive materials mentioned above for interfacial additivematerial layer 24. The interfacial additive material layer 26 may have athickness from 1 nm to 20 nm to minimize the increase of cell internalresistance. The interfacial additive material layer 26 may be formedutilizing a deposition process including, for example, chemical vapordeposition, plasma enhanced chemical vapor deposition, or atomic layerdeposition. The interfacial additive material layer 26 can maintainstructural rigidity for interfacial overlap, which enables high ionicconductivity and reduces the internal resistance of the cell. Inaddition, the interfacial additive material layer 26 can provideelectrical insulation at the interfaces of concern, preventing theleaking or shorting of the cell through spatial control of electricallyconductive components within the battery.

Referring now to FIG. 4, there is illustrated an exemplary rechargeablelithium-ion battery in accordance with a fourth embodiment of thepresent application. The exemplary rechargeable lithium-ion batteryillustrated in FIG. 4 is similar to the rechargeable lithium-ion batterystack shown in FIG. 1 except that an interfacial additive material layer24 is positioned between Porous Region 1 (i.e., the top porous layer 17)of the anode structure 12 and the electrolyte region 18, and anotherinterfacial additive material layer 26 is positioned between theelectrolyte region 18 and the lithium-containing cathode material layer20, and another dielectric material layer 26. Specifically, theexemplary rechargeable lithium-ion battery illustrated in FIG. 4includes a battery material stack of an anode current collector 10, asdefined above, an anode structure 12, as defined above, an interfacialdielectric material layer 24, as defined above, an electrolyte region18, as defined above, an interfacial dielectric material layer 26, asdefined above, a lithium-containing cathode material layer 20, asdefined above, and a cathode current collector 22, as defined above. Thebattery material stack shown in FIG. 4 may have other orientationsbesides that shown in FIG. 4. For example, it may be flipped 180°.

Referring now to FIG. 5, there is illustrated an exemplary rechargeablelithium-ion battery in accordance with a fifth embodiment of the presentapplication. The exemplary rechargeable lithium-ion battery illustratedin FIG. 5 is similar to the rechargeable lithium-ion battery stack shownin FIG. 1 except that the porous region (including Porous Region 1) andPorous Region 2)) of the anode structure 12 are patterned. The patternedporous region, including both Porous Regions 1 and 2 (not shownindividually), is designated as element 16P in FIG. 5 of the presentapplication. Specifically, the exemplary lithium-ion battery illustratedin FIG. 5 includes a battery material stack of an anode currentcollector 10, as defined above, an anode structure 12, as defined above,and having a patterned porous region 16P (including Porous Regions 1 and2), an electrolyte region 18, as defined above, a lithium-containingcathode material layer 20, as defined above, and a cathode currentcollector 22, as defined above. The battery material stack shown in FIG.5 may have other orientations besides that shown in FIG. 5. For example,it may be flipped 180°.

An interfacial additive material layer 24 may be formed between thepatterned porous region 16P and the electrolyte region 18 and/orinterfacial additive material layer 26 may be formed between theelectrolyte region 18 and the lithium-containing cathode material layer20. The patterning of the porous region (including Porous Regions 1 and2) may be performed utilizing conventional patterning techniquesincluding, for example, lithography and etching, possibly in conjunctionwith mechanical grinding/polishing, and doping. In some embodiments,patterning of the porous region (16, 17) may be performed by simpleselective doping in silicon, for example, by ion implantation, epi, orthermal doping. Patterned porous region 16P (which collectively includesPorous Regions 1 and 2) may provide a means to further increase thecapacity as well as the kinetic (power) capabilities of the anodestructure 12 of the present application. Patterned porous region 16P(which collectively includes Porous Regions 1 and 2) may also provide afaster charge rate.

Referring now to FIGS. 6A-6B, there are illustrated exemplaryrechargeable lithium-ion batteries in accordance with a sixth embodimentof the present application. The exemplary rechargeable lithium-ionbatteries illustrated in FIGS. 66A and 6B are similar to the lithium-ionbattery stack shown in FIG. 1 except that the porous region (includingPorous Region 1 and Porous Region 2) of the anode structure 12 arepatterned and the lithium-containing cathode material layer 20 is alsopatterned. The patterned porous region (including Porous Regions 1 and2) is designated as element 16P in FIGS. 6A-6B of the presentapplication, and the patterned lithium-containing cathode material layeris designated as element 20P is FIGS. 6A-6B of the present application.Specifically, the exemplary lithium-ion batteries illustrated in FIGS.6A-6B include a battery material stack of an anode current collector 10,as defined above, an anode structure 12, as defined above and having apatterned porous region 6P (including Porous Regions 1 and 2), anelectrolyte region 18, as defined above, a patterned lithium-containingcathode material layer 20P, as defined above, and a cathode currentcollector 22, as defined above. The battery material stacks shown inFIGS. 6A-6B may have other orientations besides that shown in FIGS.6A-6B. For example, they may be flipped 180°.

In one embodiment, as shown in FIG. 6A, the patterned battery materialstack components 16P and 20P oppose one another, e.g., the higherregions (lower regions) of each component face one another in the samelateral position of the battery, in a non-complimentary manner.Alternatively, the patterned battery material stack components 16P and20P may be complimentary, in shape—fitting together like lock and key,as shown in FIG. 6B. In this embodiment, the proximity of patternedelectrodes with respect to one another, in addition to electrolytethickness (electrolyte fills all space between battery components 16Pand 20P) can be controlled by aligning the opposing electrodes atspecific proximity with regard to one another. An interfacial additivematerial layer 24 may be formed between the patterned region 16P (whichcollectively includes Porous Regions 1 and 2) and the electrolyte region18 and/or interfacial additive material layer 26 may be formed betweenthe electrolyte region 18 and the patterned lithium-containing cathodematerial layer 20P.

The patterning of the lithium-containing cathode material layer 20P maybe performed utilizing conventional patterning techniques including, forexample, lithography and etching, or by utilizing a lift-off process.The patterned lithium-containing cathode material layer 20P may becomplementary or non-complementary with respect to the patterned porousregion 16P. The patterned lithium-containing cathode material layer 20Pmay provide a further increase the capacity as well as the kineticcharge/discharge capabilities of the lithium-ion battery of the presentapplication. Collectively, the patterned the porous region 16P (whichcollectively includes Porous Regions 1 and 2) and the patternedlithium-containing cathode material layer 20P may provide maximizedbattery capacity and, possible increase the charge rate of thebattery—as pattern dimensions, along with final fixed proximity ofspatial volume between the patterned porous region 16P (whichcollectively includes Porous Regions 1 and 2) and the patternedlithium-containing cathode material layer 20P may impact and determinethe thickness, density and other physical properties of the electrolyteregion 18—thereby directly affecting ion-electron-mobility propertiesthroughout the battery stack.

Referring now to FIG. 7A, there is illustrated a schematic whichillustrates the overall process of utilizing a crystalline p-typesilicon material 50 for the anodic etching method described herein.Notably, the process begins by providing a crystalline p-type siliconmaterial 50, and then performing anodic etching which provides an anodestructure that includes Porous Region 1 (PR1) (i.e., the top porouslayer 17) and Porous Region 2 (PR2) (i.e., the bottom porous layer 16)along with a non-etched portion of the original crystalline p-typesilicon substrate residing below the two porous regions. The non-etchedportion of the original substrate defines the non-porous region 14 ofthe silicon substrate. In this drawing, the non-porous region 14 is alsodesignated as element 50S; it is noted that non-porous 50S has the samecharacteristics as non-porous region 14 mentioned above.

FIG. 7B is a transmission electron micrograph (TEM) (though across-sectional view) of an experimentally fabricated porous siliconsubstrate, such as the one illustrated in FIG. 7A. This TEM micrographclearly illustrates the two porous regions, PR1 (i.e., the top porouslayer 17), and PR2 (i.e., bottom porous layer 16), illustrated in FIG.7A with the Porous Region 1 having a thickness on the order of about 30nm, and Porous Region 2 being far thicker than Porous Region 1.

FIG. 8A is a high resolution transmission electron micrograph of oneembodiment of the porous silicon material referred to herein in FIG. 7A.The scale line in this figure illustrates the total thickness of PorousRegion 1 being about 29 nm. FIG. 8B is a secondary ion mass spectroscopy(SIMS) profile of the porous silicon material shown in FIG. 8A. ThisSIMS profile illustrates the relatively low concentrations of carbon,oxygen and fluorine elements in the first 30 nm of the porous siliconmaterial—which correlates directly with Porous Region 1 (as indicated bythe dashed boxes in FIG. 8A and FIG. 8B connected via a double sidedarrow).

Referring now to FIGS. 9A-9F, there are shown a sequence of steps as aflow diagram, showing a porous silicon electrode (i.e., an anodestructure including non-porous region 50S, Porous Region 2 (PR2) andPorous Region 1 (PR1)) and the operation of charge storage via theelectrode material when a liquid-based electrolyte is used, with a seedlayer 52 during charge and discharge cycles, accompanied with SEM imagesof a porous silicon electrode at 5 cycles (FIG. 9D) and at about 250cycles (FIG. 9F). Notably, FIG. 9A illustrates a porous siliconelectrode, as described and illustrated in FIG. 7A, prior to itsincorporation into an electrochemical energy storage cell. The poroussilicon electrode includes non-porous region 50S, Porous Region 2 (PR2)and Porous Region 1 (PR1). FIG. 9B is an illustration of the initiallithiation process of the porous silicon electrode when incorporatedinto a Li-ion electrochemical energy storage cell. During the initialexposure of the porous silicon electrode to the lithium ion containingelectrolyte and/or during the initial time period of electrochemicallylithiating the porous silicon electrode and/or during the initialcharging of the porous silicon electrode, planar lithium-containing seedlayer 52 formation occurs. As is shown, the lithium-containing seedlayer 52 is located atop Porous Region 1 and a portion of the seed layer52 may, in some embodiments, extend into an upper portion of PorousRegion 2. The topmost surface of the seed layer 52 is typically flat,i.e., planar. FIG. 9C is a schematic illustration of the planar lithiumplating occurring during the charging process. In FIG. 9C, element 54denotes the planar lithium layer that forms during this operationalstep. It is noted that when the battery reaches full charge thethickness of the plated lithium metal 54 on the seed layer 52 isproportional to the amount of lithium deintercalated from thelithium-containing cathode material layer and as transferred from theelectrolyte, as determined by a working voltage range.

FIG. 9D is a scanning electron micrograph cross section of a poroussilicon electrode demonstrating the plating phenomena illustrated inFIG. 9C; where the cross-section image of the electrode is taken in thecharged state after about 250 charge/discharge cycles. Lithiumpenetration is observed through Porous Region 1 but only in the topportion of Porous Region 2 in the charge state causing some cracks inupper parts of Porous Region 2. FIG. 9E is an illustration of thelithium de-plating occurring during the discharge process, where aportion of irreversibly plated lithium metal 54 on top of the seed layer52 remains. Due to the discharge, the thickness of the remaining portionof the plated lithium metal 54 is substantially less than the thicknessof planar lithium layer 54 formed during the charge state, as shown inFIG. 9C. It is noted that as the battery approaches a sustainabledischarge state the thickness of the layer of lithium metal decreasesproportionally, as determined by the working voltage range. FIG. 9F is ascanning electron micrograph cross-section of a porous silicon electrodein the discharge state which has been charged and discharged fivetimes—corresponding to FIG. 9E. In one embodiment, the working voltagerange is between 4.2V to 3.0V. In one embodiment, the lithium-containingcathode material layer is a lithium cobalt oxide. The above seed layerformation and lithium metal plating that occurs during charging, and thesubsequent deplating of lithium metal that occurs during discharging isobserved for lithium-ion batteries that contain a solid-stateelectrolyte or liquid electrolyte or any other type of electrolytementioned herein.

In some embodiments, the rechargeable lithium-ion battery of the presentapplication can be charged and discharged over 200 cycles, whenutilizing a sustainable working voltage, such as them one mentionedabove. After 200 charge and discharge cycles, the surface of the platedlithium metal is nominally continuously planar, on average.

Referring now to FIGS. 10A-10D, there are shown actual SEM images for anall solid-state lithium ion battery in accordance with the presentapplication and containing a structure similar to that shown in FIG. 1in which the electrolyte region 18 is a solid-state material such as,for example LiPON. The structure also includes anode structure 12 shownas shown in FIG. 1 or FIG. 9A. Notably, FIG. 10A is a SEM of thestructure prior to galvanostatic-or-potentiostatic-induced charge ordischarge, FIG. 10B is another SEM of the structure after 6 charge anddischarge cycles, and FIG. 10C is yet another SEM image of the structureafter 56 charge and discharge cycles.

The SEM of FIG. 10A is a cross-section SEM image of the all-solid statebattery, prior to galvanostatically or potentiostatically inducingelectrochemical charge or discharge, showing a porous silicon electrode(i.e., an anode structure including non-porous region (not shown) PorousRegion 2 (PR2) and a planar Porous Region 1 (PR1)), where a solidelectrolyte region 18 resides above the Porous Region 1 (PR1). FIG. 10Bis a cross-section SEM image of the all solid state cell illustrated inFIG. 10A, after 6 galvanostatically induced charge and discharge cycles,where, from bottom to top, Porous Region 2 (PR2), a Porous Region 1(PR1) containing a lithium-containing seed layer 52 are observed.Notably, off-white features emanating from the Porous Region 1(PR1)/solid electrolyte region 18 interface are clearly observed, wherethe features are thought to represent the reaction of air with thelithium rich material that comprised the lithium-containing seed layer52 and/or comprised the plated lithium metal residing on thelithium-containing seed layer 52 which formed during the 6charge/discharge cycles. FIG. 10C is a cross-section SEM image of theall solid state cell illustrated in FIG. 10A, after 67 galvanostaticallyinduced charge and discharge cycles, where from bottom to top, thesubstantially original Porous Region 2 (PR2), a partially lithiatedPorous Region 2 (PR2), a planar formation of lithium metal containingdendrite features mixed with solid-state electrolyte material in thePorous Region 1 (PR1) and the electrolyte region 18 are observed. Duringthe initial exposure of the porous silicon electrode to the lithium ioncontaining electrolyte and/or during the initial time period ofelectrochemically lithiating the porous silicon electrode and/or duringthe initial charging of the porous silicon electrode, a planarlithium-containing seed layer 52 formation occurs. As is shown, thelithium containing seed layer 52 is located in the Porous Region 1 areaand a portion of the seed layer 52 may extend into an upper portion ofPorous Region 2. The topmost surface of the seed layer 52 is typicallyflat, i.e., planar, as observed in FIGS. 10A and 10B where PR1 and theseed layer 52 is in a planar, intimate contact with the electrolyteregion 18, prior to cycling. This planar, lithium metal containing seedlayer is thought to act as a host or nucleation site for subsequentplating/stripping of lithium metal during subsequent charge/dischargecycles, respectively. After 6 charge/discharge cycles, the lithium richmaterial which forms the seed layer and/orlithium-metal-plated-seed-layer, is altered from its immobilized, planarstate upon destruction and cleaving of the cell in order to obtain theSEM image of FIG. 10B—where this respective lithium metal containinglayer now reacts with ambient air chemistry, forming the off-whitefeatures which are observed emerging/emanating from the PR1/solidelectrolyte region 18 interfacial region. In FIG. 10D, after 56charge/discharge cycles, a substantially original Porous Region 2 (PR2)area is observed, above which a partially lithiated Porous Region 2 isobserved (PR2), above which an approximately 183 nm planar layer oflithium-rich dendrite-type formations are observed in the Porous Region1 (PR1) area, above which the LiPON electrolyte area is observed.Notably, the observation of the planar formation of lithium-richdendrite features in/on the Porous Region 1 (PR1) region, which remainstable upon destruction and cleaving of the cell after 67charge/discharge cycles, where intimate, continuous contact between thesolid electrolyte region 18 and the lithium metal rich dendrite featuresin/on the Porous Region 1 (PR1) area, illustrates the high efficacy ofthe present invention as a stable lithium metal hosting porous siliconanode in all-solid-state batteries, in addition to liquid electrolytecontaining stable lithium metal hosting porous silicon anode comprisingbatteries, as illustrated in FIGS. 9A-9F.

In some embodiments, and upon multiple charge/discharge cycles, inaddition to dendrite formation at the lithium metal/electrolyteinterface, a unique dendrite formation occurs on/along the (111) crystalsilicon planes at the bottom porous layer/top porous layer interface.

The rechargeable lithium-ion batteries illustrated in FIGS. 1-5, 6A and6B may have any size and/or shape. One example range includes: 10 μm toless than 1 mm (small) and large is anything above 1 mm. In one example,the size of the rechargeable lithium-ion batteries may be 100 μm×100μm×100 μm. In another example, the size of the rechargeable lithium ionbatteries may be 50 mm×50 mm×5 mm. In some embodiments, in which asemiconductor base substrate is present, the rechargeable lithium-ionbatteries illustrated FIGS. 1-5, 6A and 6B may be integrated withsemiconductor devices including for example, transistors, capacitors,diodes, laser diodes, light emitting devices, photovoltaic devices,central processing units, silicon based device structures, etc. Thebattery which powers the semiconductor devices, could both be on thesame side or opposite side of the semiconductor substrate.

Integration may be performed in two ways: 1) Conventionally bypreliminary patterning, lithography, etching of the semiconductorsubstrate prior to anodization and creation of porous semiconductorregion, or 2) Via selective doping such as ion implantation andsubsequent thermal annealing, such as furnace or lamp or laserannealing, or selective epitaxial growth, etc. Devices can be placed onsame original semiconductor substrate or can be integrated with the sameoriginal semiconductor substrate or on an adjoined semiconductorsubstrate within a given working proximity (same side or opposite sideof battery are possibilities).

The method of fabricating the anode structure 12 of the presentapplication is now discussed in greater detail. The method of thepresent application provides 1) the “growth” or production or etching ofa porous semiconductor region connected to a non-porous semiconductorregion (such as a single crystalline silicon material) which can then beintegrated into /with other silicon based technologies, 2) thesuccessful integration and use of liquid, solid and semi-solidelectrolytes and their high functioning capability in rechargeablebatteries (versatile with any electrolyte), and 3) the thickness of thesolid state electrolyte can be controlled in nm regime due to thespecular and smooth surface of the starting silicon substrate whichenables high control of battery performance, charge rate, ion mobility,and is compatible with physical deposited electrolytes.

Notably, the anode structure 12 of the present application can be madeusing an anodization process in which a substrate including at least anupper region of a p-type silicon material is immersed into a solution ofconcentrated HF (49%) while an electrical current is applied with aplatinum as the anode and the substrate as the cathode. The anodizationprocess is performed utilizing a constant current source that operatesat a current density from 0.05 mA/cm² to 150 mA/cm², wherein mA ismilli-Amperes. In some examples, the current density is 1 mA/cm², 2mA/cm², 5 mA/cm², 50 mA/cm², or 100 mA/cm². In a preferred embodiment,the current density is from 1 mA/cm² to 10 mA/cm². The current densitymay be applied for 1 second to 5 hrs. In some examples, the currentdensity may be applied for 5 seconds, 30 seconds, 20 minutes, 1 hour, of3 hours. In an embodiment, the current density may be applied for 10seconds to 1200 seconds, specifically for the doping level in the range10¹⁹cm³ range. The anodization process is typically performed at nominalroom temperature from (20° C.) to 30° C.) or at a temperature that isslightly elevated from room temperature. Following the anodizationprocess, the structure shown in FIG. 7B is typically rinsed withdeionized water and then dried.

In some embodiments, and after anodiziation, the anode structure 12 maybe cut into a desired dimension prior to being used. In someembodiments, the anode structure 12 may be placed upon and, optionally,bonded to the anode current collector, 10 as defined above, andthereafter the various other components of the lithium-ion battery maybe formed. In other embodiments, the anode structure 12 may be placedupon and, optionally bonded to, the electrolyte region 18 of apre-fabricated battery material stack that also includes a cathoderegion that includes a lithium-containing cathode material layer 20 anda cathode current collector 22.

Referring now to FIG. 11, there is illustrated a flow chart showing oneembodiment for making the anode structure 12 of the present application.Notably, the anode structure 12 including the Porous Region 1 and PorousRegion 2 and the non-porous region 14 (or 50S) discussed above can beformed utilizing the processing steps shown in FIG. 11. In oneembodiment, the substrate 12 may be entirely composed of a p-type dopedcrystalline silicon material, while in other embodiments, other siliconmaterials or germanium (both doped or undoped) may be present beneaththe p-type doped silicon material. The method may include in a firststep, i.e., Step 1 (70), of cleaning the p-doped silicon substrate witha mixture of ammonium hydroxide, deionized water and hydrogen peroxide(5:1:1 v/v) at 60° C. to 80° C. for approximately 10 minutes. Next, andin Step 2 (72), the cleaned p-doped silicon substrate is immersed in 49%hydrofluoric acid and thereafter an electrical current is appliedthereto to begin electrochemical anodization (i.e., anodizing etching).In one embodiment, the applied current is a constant current in a rangeof 1 mA/cm² to 10 mA/cm². In Step 3 (74), the anodizing etch continuesusing the following electrochemical anodization conditions: nominal roomtemperature (20° C. to 30° C.) and less than or equal to 5mA/cm² for 10s to 2000 s. After etching, and in Step 4 (76), the etched siliconsubstrate is rinsed with deionized water and the dried. The anodizationprocess defined in Step 3 converts an upper portion of the substratecontaining the p-doped silicon into Porous Region 1 and Porous Region 2and the underlying substrate is not affected by the anodization processand forms the non-porous region 14 (or 50S) described above.

In any of the embodiments mentioned above and, as illustrated in FIGS.1-5, 6A and 6B, the lithium-containing cathode material layer 20 maycontain grains having a grain size of less than 100 nm, and a density ofgrain boundaries of 10¹⁰ cm⁻² or greater. In some embodiments, the grainsize of the individual grains that constituent the lithium-containingcathode material layer 20 is from 1 nm to less than 100 nm. In someembodiments, the density of boundaries can be from 10¹⁰ cm⁻² to 10¹⁴cm⁻². The term “grain boundary” is defined herein as an interfacebetween two grains of materials. The grain boundaries are present in thelithium-containing cathode material layer 20 in a somewhat randomorientation. Some of the grain boundaries may extend completely throughthe cathode material such that one end of the grain boundary is presentat a bottommost surface of the cathode material and another end of thegrain boundary is located at a topmost surface of the cathode material.In this embodiment, the grain boundaries are not oriented perpendicularto the topmost and bottommost surface of the lithium-containing cathodematerial layer 20.

In any of the embodiments mentioned above and, as illustrated in FIGS.1-5, 6A and 6B, the lithium-containing cathode material layer 20 mayhave a columnar microstructure having columnar grain boundaries. Thecolumnar grain boundaries are oriented perpendicular to the topmostsurface and the bottommost surface of the lithium-containing cathodematerial layer 20. In such an embodiment, the lithium-containing cathodematerial layer 20 has a plurality of fin-like structures within thecathode material. The lithium-containing cathode material layer 20having the columnar microstructure has a grain size of less than 100 nm,and a density of columnar grain boundaries of 10¹⁰ cm⁻² or greater. Insome embodiments, the grain size of the individual grains thatconstituent the lithium-containing cathode material layer 20 is from 1nm to less than 100 nm. In some embodiments, the density of columnargrain boundaries can be from 10¹⁰−10¹⁴ cm⁻². In one embodiment, theelectrically conductive cathode material is a lithium-containingmaterial as defined above.

The presence of a lithium-containing cathode material layer 20 thatcontains grains having a grain size of less than 100 nm, and a densityof grain boundaries of 10¹⁰ cm⁻² or greater, or a lithium-containingcathode material layer 20 having the columnar microstructure with theanode structure 12 of the present application in a rechargeable batterymaterial stack as shown for example, in FIGS. 1-5, 6A and 6B of thepresent application facilitates fast and substantially or entirelyvertical ion, i.e. Li-ion, transport which can lead to fast chargingbatteries.

Rechargeable batteries that contain anode structure 12 and alithium-containing cathode material layer 20 which contains grainshaving a grain size of less than 100 nm, and a density of grainboundaries of 10¹⁰ cm⁻² or greater, or a lithium-containing cathodematerial layer 20 having the columnar microstructure may exhibit acharge rate of 5 C or greater, wherein C is the total battery capacityper hour. In some embodiments, the charge rate of the batteries thatcontain anode structure 12 and a lithium-containing cathode materiallayer 20 which contains grains having a grain size of less than 100 nm,and a density of grain boundaries of 10¹⁰ cm⁻² or greater, or alithium-containing cathode material layer 20 having the columnarmicrostructure can be from 5 C to 1000 C or greater. Also, rechargeablebatteries that contain the anode structure 12 and a lithium-containingcathode material layer 20 that contains grains having a grain size ofless than 100 nm, and a density of grain boundaries of 10¹⁰ cm² orgreater, or a lithium-containing cathode material layer 20 having thecolumnar microstructure may have a capacity of 100 mAh/gm of cathodematerial or greater.

The lithium-containing cathode material layer 20 that contains grainshaving a grain size of less than 100 nm, and a density of grainboundaries of 10¹⁰ cm² or greater, or the lithium-containing cathodematerial layer 20 having the columnar microstructure may be formedutilizing a sputtering process. In some embodiments, and following thesputtering of the cathode material, no subsequent anneal is performed;the cathode material that is sputtered without annealing provides alithium-containing cathode material layer 20 that contains grains havinga grain size of less than 100 nm, and a density of grain boundaries of10¹⁰ cm⁻² or greater. In other embodiments, and following the sputteringof the cathode material, an anneal may be performed to provide alithium-containing cathode material layer 20 having the columnarmicrostructure. Annealing is performed at a temperatures less than 300°C. to preserve the charge rate of greater 5 C. In one embodiment,sputtering may include the use of any precursor source material orcombination of precursor source materials. In one example, a lithiumprecursor source material and a cobalt precursor source material areemployed in forming a lithium cobalt mixed oxide. Sputtering may beperformed in an admixture of an inert gas and oxygen. In such anembodiment, the oxygen content of the inert gas/oxygen admixture can befrom 0.1 atomic percent to 70 atomic percent, the remainder of theadmixture includes the inert gas. Examples of inert gases that may beused include argon, helium, neon, nitrogen or any combination thereof.

The lithium-containing cathode material layer 20 that contains grainshaving a grain size of less than 100 nm, and a density of grainboundaries of 10¹⁰ cm² or greater, or the lithium-containing cathodematerial layer 20 having the columnar microstructure may have athickness from 10 nm to 20 μm. Other thicknesses that are lesser than,or greater than, the aforementioned thickness values may also be usedfor the lithium-containing cathode material layer 20 that containsgrains having a grain size of less than 100 nm, and a density of grainboundaries of 10¹⁰ cm⁻² or greater, or the lithium-containing cathodematerial layer 20 having the columnar microstructure. Thicklithium-containing cathode material layer 20 that contains grains havinga grain size of less than 100 nm, and a density of grain boundaries of10¹⁰ cm² or greater, or the lithium-containing cathode material layer 20having the columnar microstructure can provide enhanced battery capacitysince there is more area, i.e., volume, to store the battery charge.

While the present application has been particularly shown and describedwith respect to preferred embodiments thereof, it will be understood bythose skilled in the art that the foregoing and other changes in formsand details may be made without departing from the spirit and scope ofthe present application. It is therefore intended that the presentapplication not be limited to the exact forms and details described andillustrated, but fall within the scope of the appended claims.

What is claimed is:
 1. A battery comprising: a lithium-containingcathode material layer; an anode structure of unitary construction andincluding a non-porous region and a porous region comprising a topporous layer having a first thickness and a first porosity, and a bottomporous layer located beneath the top porous layer and forming aninterface with the non-porous region, wherein at least an upper portionof the non-porous region and the entirety of the porous region arecomposed of silicon, and wherein the bottom porous layer has a secondthickness that is greater than the first thickness, and a secondporosity that is greater than the first porosity; and an electrolyteregion located between the top porous layer of the anode structure andthe lithium-containing cathode material layer.
 2. The battery of claim1, wherein the top porous layer, the bottom porous layer, and thenon-porous region are entirely composed of silicon.
 3. The battery ofclaim 2, wherein the silicon is single crystalline.
 4. The battery ofclaim 1, wherein a lower portion of the non-porous layer is composed ofdoped silicon or a doped silicon germanium alloy having a germaniumcontent of less than 10 atomic percent.
 5. The battery of claim 1,wherein the first porosity of the upper porous layer has an average poreopening of less than 3 nm, and wherein the second porosity of the bottomporous layer has an average pore opening of greater than 3 nm.
 6. Thebattery of claim 1, wherein the first thickness of the top porous layeris 50 nm or less.
 7. The battery of claim 1, wherein the secondthickness of the bottom porous layer is between 0.1 μm to 20 μm.
 8. Thebattery of claim 1, wherein the non-porous region is composed of p-dopedsilicon that is single crystalline.
 9. The battery of claim 1, whereinthe non-porous region and the porous regions are entirely comprised ofp-type doped silicon.
 10. The battery of claim 1, wherein the silicon isp-doped silicon having a p-type dopant concentration in a range of 10¹⁹cm⁻³.
 11. The battery of claim 1, wherein the silicon is boron-dopedsilicon.
 12. The battery of claim 1, further comprising an anode currentcollector contacting a surface of the non-porous region of the anodestructure.
 13. The battery of claim 1, further comprising a cathodecurrent collector electrode contacting a surface of thelithium-containing cathode material layer.
 14. The battery of claim 1,wherein the electrolyte region is composed of a solid-state electrolyte,a liquid electrolyte, a semi-solid electrolyte, an originally liquidthen becoming solid electrolyte, a gel electrolyte, a polymer-containingelectrolyte, a composite cathode/electrolyte combination, or anycombination thereof.
 15. The battery of claim 1, wherein the electrolyteregion is entirely composed of a solid-state electrolyte.
 16. Thebattery of claim 1, further comprising an interfacial additive materiallayer located between the top porous layer of the anode structure andthe electrolyte region.
 17. The battery of claim 1, further comprisingan interfacial additive material layer located between the electrolyteand the lithium-containing cathode material layer.
 18. The battery ofclaim 1, further comprising a first interfacial additive material layerlocated between the top porous layer of the anode structure and theelectrolyte region, and a second interfacial additive material layerlocated between the electrolyte and the lithium-containing cathodematerial layer.
 19. The battery of claim 1, wherein the porous regionincluding the top and bottom porous layers are patterned.
 20. Thebattery of claim 19, wherein the lithium-containing cathode materiallayer is patterned.
 21. The battery of claim 1, wherein the porousregion is located at the top, bottom or side of any three-dimensionalstructure.